1. Field of the Invention
This invention relates to cyclotrons and, more particularly to a cyclotron system and method for sensing and monitoring the operation of the cyclotron and the synthesis of a radioisotope into a positron-emitting radio chemical.
2. Description of Related Art
Radioisotope delivery systems have been found to be a cost effective and easy way to automatically produce up to Curie levels of positron-emitting radioisotopes in compounds in a variety of chemical forms. One popular radioisotope delivery system is the CTI RDS-112 Cyclotron which is manufactured by CTI, Inc. of Knoxville, Tenn. and which is available from Siemens Gammasonics, Inc. The standard radioisotope delivery system configuration includes a cyclotron, inter-locking shield, four targets for the production of .sup.11 C, .sup.13 N, .sup.15 O and .sup.18 F, target utility systems and a chemical synthesis module or unit. The system is fully automated from a cold start to the beginning of isotope production.
The positron-emitting radio chemical, such as .sup.18 F-labeled 2-deoxyglucous may subsequently be injected into a patient and imaged in a positron emission tomography ("PET") scanner. The PET scanner has been found to be useful in providing tomographic images of, for example, a patient's brain.
PET scans are often interrupted, delayed or canceled altogether due to the problems associated with producing the .sup.18 F positron-emitting isotope. This, in turn, results in inconvenience to the patient and delays in diagnosing and treatment of an illness.
Some portion of the delays or cancellations have occurred due to power fluctuations at the facility where the cyclotron is located. The power fluctuations have caused the vacuum pumps, for example, associated with the cyclotron to fail which causes a cyclotron acceleration chamber to loose its vacuum. This, in turn, interrupts the production of the radioisotope which is required to produce the radio chemical.
Another cause of the cancellations or delays have resulted from shooting or accelerating, for example, a "dry" .sup.18 F water target (i.e., the target volume not containing target material when exposed to accelerated ions). If the cyclotron continued to accelerate ions towards the "dry" .sup.18 F water target, the target must be rebuilt which necessitates several hours of rebuild time and downtime.
In the past, target pressure readings associated with a target were used to attempt to monitor this fault condition. The problem with the pressure readings was that they were inaccurate indicators of a target fault and that they required an operator to be present to observe a monitor of the cyclotron.
Other cancellations and delays in the PET scans resulted from failures of the synthesis module in the cyclotron during synthesizing the radioisotope into the positron-emitting radio chemical. The typical production of a positron-emitting radio pharmaceutical from the synthesis module typically took on the order of about 2 hours. After such time, the radio chemical was removed from the synthesis module of the cyclotron and subsequently used in the PET scan. It was sometimes encountered that the synthesis could not proceed properly and, consequently, the desired radio pharmaceutical was not synthesized. Unfortunately, there was no hands-free and convenient way to continuously monitor and observe the synthesis operation.
What is needed, therefore, is a system and method for sensing and monitoring the targets, the vacuum state of the acceleration chamber, as well as the synthesis procedure during the production of the positron-emitting radio chemical.